This invention relates to disinfecting lenses, such as contact lenses. In particular, the invention relates to methods and compositions useful to quickly and effectively disinfect lenses while reducing eye irritation caused by disinfecting the lenses.
Contact lenses should be periodically disinfected to protect the wearer's eyes from infection and to improve the wearer's comfort. It is often desirable that lens disinfecting be accomplished quickly, e.g., for the convenience of the wearer. However, conventional fast-acting disinfectants that are used with contact lenses have a high potential to cause eye irritation. In fact, the general rule has been that the amount of eye irritation to be expected is directly proportional to the rate of disinfecting. Fast-acting disinfectants, such as hydrogen peroxide, cause significant ocular irritation if placed directly in the eye. Thus, when using such disinfectants a thorough rinsing and/or neutralization step is required to remove substantially all traces of the disinfectant. Thus, in Gaglia, et al U.S. Pat. No. 3,912,451 a metal component is used to remove hydrogen peroxide from soft contact lenses which have been sterilized with hydrogen peroxide. Also, such disinfectants are often not stable and tend to lose their potency over time. A fast-acting, stable lens disinfecting system which is not as prone to cause eye irritation would clearly be advantageous.
It has been proposed to disinfect substrates using an acidic solution containing chlorites, such as sodium chlorite. Alliger U.S. Pat. No. 4,084,747 and International Patent Publication (PCT) No. WO35/04107 are directed to such systems. The acidic conditions apparently cause liberation of chlorine dioxide, which acts as a disinfectant. Lenses, and in particular contact lenses, have not been disclosed as being disinfected in such acidic media. High acidity can cause substantial eye irritation.
Randeri et al U.S. Pat. No. 3,873,696 discloses a system for sterilizing hydrophilic contact lenses with an aqueous, isotonic solution containing an oxygen releasing salt such as potassium peroxymonosulfate or certain chlorine compounds, such as hypochlorites, chlorites, chlorates and perchlorates. Because of the relatively low antimicrobial activity of these sulfur-containing salts or chlorine compounds alone, relatively high concentrations of these materials are needed to provide the desired contact lens treatment in a reasonable period of time. This patent does not disclose the formation of contact lens disinfecting amounts of chlorine dioxide.
In addition to disinfecting the contact lens, it should also be cleaned, e.g., of debris such as protein-based debris which accumulates on the lens during use. Such lens cleaning is often done in the presence of one or more enzymes. See, for example, Karageozian U.S. Pat. No. 3,910,296. In many instances, a complete lens maintenance procedure involves first enzymatic cleaning followed by the separate lens disinfecting step. One system in which lens cleaning and disinfecting occur substantially simultaneously is disclosed in Huth, et al U.S. Pat. No. Re. 32,672. This system employs a solution to contact the lens which comprises a disinfecting amount of peroxide and an effective amount of peroxide-active proteolytic enzyme for a time sufficient to remove substantially all protein accretions and to disinfect the lens.